Warm the water in a saucepan over medium heat, and stir in the sugar until it dissolves fully. Cool the sugar water to room temperature.
Drop the ginger into a pint-sized jar, and then cover it with the sugar water. Seal the jar, and let it culture at room temperature for one day.
The next day, and each day for 5 days, stir 1 teaspoon sugar and ½ ounce ginger into the jar, and then close the jar tightly. Between 3 and 5 days, you should start to see bubbles forming, and your bug should smell yeasty and gingery. When you see bubbles, your bug is ready to use.
To use the bug, strain ½ cup of the liquid and mix it with 7 ½ cups liquid such as fruit juice or sweetened herbal tea, bottle and ferment up to 3 days.
